DETERMINATION OF CERTAIN ANTIHISTAMINES THROUGH TERNARY COMPLEX-FORMATION

Antihistamines, namely terfenadine and chlorphenoxamine hydrochloride, react with cobalt and thiocyanate ions to give ternary complexes. These complexes are readily extractable in benzene to give a blue colour with maximum absorption at 625nm. which can be used for quantitative spectrophotometric analysis. The mean recoveries for authentic samples of terfenadine and chlorphenoxamine hydrochloride were 99.9 +/- 0.3 S.E. and 99.9 +/- 0.3 respectively (P = 0.05). Alternatively, determination of cobalt content of the benzene extract via atomic absorption spectroscopy provides an indirect method for the determination of these antihistamines. The mean recoveries were 99.33 +/- 0.3 and 99.19 +/- 0.3 respectively. Both methods were applied to the analysis of pharmaceutical preparations, the results obtained agreed well with those obtained by official methods.